Lighting diffuser



FIG. 1 is a top and front perspective view of a lighting diffuser according to the present design;

FIG. 2 is a left-side view thereof, the right-side view, front-side view, and back-side views are identical to the left-side view shown;

FIG. 3 is a top view thereof; and,

FIG. 4 is a bottom view thereof.

The broken lines in the drawings of the lighting diffuser form no part of the claimed design. 

CLAIM The ornamental design for a lighting diffuser, as shown and described. 